This invention relates generally to ski structure and, more particularly, to a new ski structure formed of a composite material.
Modern skis must have very precise mechanical characteristics. More particularly, the rigidity of modern skis both in flection (bending) and torsion at every point on the ski must be well defined. More particularly, modern skis must be so constructed that the values of the rigidities in both torsion and in flection permit improved disengagement as well as improved performance in turns while at the same time being sufficiently great so as to maintain the structural integrity of the ski.
Further, it is important that the ski exhibit satisfactory vibratory behavior. More particularly, it is important for a ski when subjected to shocks to vibrate in a manner such that the natural frequency of such vibrations will be relatively high, so that the amplitude of the vibration under a given shock will be low and so that the natural damping of the ski will be substantial.
Many ski constructions heretofore proposed satisfy the first two of these conditions, namely such skis have both good flection and torsional characteristics. However, such conventional skis do not provide satisfactory vibration characteristics. In particular, skis having a composite structure which include a core formed of wood and/or rigid synthetic foam, and/or stressed or non-stressed cellular structures, and/or stressed or non-stressed polymerized materials, disposed between a pair of layers of resin impregnated glass fibers, are known. Such skis have good torsion and bending strength characteristics. However, the vibratory characteristics of such known skis are not entirely satisfactory.
For example, ski structure is disclosed in French Pat. No. 2,099,443 which comprises a honeycomb core, a layer of fibers oriented longitudinally with respect to the ski and affixed on the upper and lower faces of the core, and at least one layer of fibers wound in a spiral around the core which is provided with two layers of longitudinally extending fibers. Although such structure has good static mechanical properties, a substantial longitudinal force is transitted to the edge of the ski structure. In order to overcome this drawback, edge members are required which are discontinuous or flexible and which are formed of a plurality of metal strands wound in a spiral configuration. Such edge members are, however, relatively complicated in construction, fragile with respect to bias shocks, and unduly add to the weight of the ski without substantially increasing its rigidity. This increase in weight contributes to a reduction in the vibratory qualities of the ski.